A bearing unit of the above-described type is disclosed in DE-GM No. 8126302, wherein the pump rotor is installed inside a bearing ring of a rotating component, such as a toothed gear, a belt pulley or the like. This known bearing unit is compactly built and is adapted for use with fluid pumps. When gaseous fluid is to be extracted from the pump, generally larger pump rotors are necessary. However, sufficiently large rotors cannot always be accommodated inside the bearing ring according to the known bearing unit. Thus, the known bearing unit often cannot be outfitted with the pump rotor of a vane-cell pump, such as that used in a motor vehicle to produce a vacuum.